EFFICACY OF FUNGICIDES FOR CONTROLLING EARLY BLIGHT OF TOMATO
Islam, Kawser-E- Jahan and S. Ali. 2012. Efficacy of fungicides for controlling early blight of tomato. Bangladesh J. Plant Pathol. Vol. 28 (1&2): 25-27.
Eight fungicides namely Pipertax 50WP (Copper Oxychloride), Mancothane 80WP (Mancozeb), Meena 80WP (Mancozeb), Sazid 70WP (Mancozeb + Metalaxyl 7%), Media 80WP (Mancozeb), Win 77WP (Copper Hydroxide), Bicozeb 80WP (Mancozeb) and Rovral 50WP (Iprodion) were tested for their effectiveness against early blight (Alternaria solani) of tomato (Lycopersicon esculentum). The fungicides were applied as foliar spray at the rate 0.2% suspension in water for 4 times at 12 days interval starting from first appearance of symptoms. All the fungicides significantly reduced disease severity and increased fruit yield and yield components compared to control. Among the fungicides tested, the highest disease reduction with maximum fruit yield and yield components were obtained with Bicozeb, which was similar to Rovral as a standard check. Reduction of disease severity and increase of fruit yield in different farms by Bicozeb ranged 58-70% and 27-49% respectively. Rovral also gave 58-70% disease reduction and 27-57% yield increase. Other fungicides reduced disease severity by 44-69% and increase in fruit yield by 4-44% over control.
Tomato (Lycopersicon esculentum Mill.) is a widely cultivated popular vegetable crop in Bangladesh. It is cultivated in about 18,800 hectares producing about 143,000 metric tons (Anon. 2008). The average yield of tomato is 7.6 t/ha, which is far below the average yields in other countries. Diseases are the major constraints for sustainable yield of crops causing about 30-40% losses annually (Rahman et al. 2001). A number of diseases attack tomato in Bangladesh. Of those, early blight caused by Alternaria solani is the most prevalent throughout the tomato growing areas of the country (Meah and Khan 1987). Crop disease control with chemicals is very popular because of its quick action, broad spectrum activity and easy availability to the growers. Different fungicides have been successfully used in controlling Alternaria blights of mustard, cabbage and cauliflower (Hossain and Mian 2004, Kudrati Khuda et al. 2003, Kohinoor et al. 2003, Rahman 2000). However, limited information is available about the fungicidal control of tomato early blight in Bangladesh (Meah 1994). An attempt was, therefore, made to evaluate the effectiveness of eight newly imported fungicides against early blight of tomato.
MATERIALS AND METHODS
The fungicides tested in the present investigation were Pipertax 50WP (Copper Oxychloride), Mancothane 80WP (Mancozeb), Meena 80WP (Mancozeb), Sazid 70WP (Mancozeb + Metalaxyl 7%), Media 80WP (Mancozeb), Win 77WP (Copper Hydroxide), Bicozeb 80WP (Mancozeb) and Rovral 50WP (Iprodion). There were altogether nine treatments including a control (plain water). Rovral 50WP was included as a standard. The fungicides were applied as foliar spray at 0.2% suspension in water. Spraying was started immediately after the onset of disease and a total of four sprays were applied at an interval of 12 days.
The experiment was conducted at the Central Research Farms of Bangladesh Agricultural Research Institute (BARI), Gazipur and Regional Agricultural Research Station (RARS), BARI, Rangpur during the winter season of 2006-2007. Cultivation procedures of tomato and doses of manure and fertilizers were the same as recommended by BARI (Razzaque et al. 2000). The unit plot size was 2.0 m x 1.2 m and line to line and plant to plant distances were 60 cm and 40 cm, respectively. Distance between blocks and between plots was 1.0 m. The experiment was laid out in a randomized complete block design with 3 replications. Fifty centimeter wide and 30 cm deep drain was made surrounding each block to facilitate irrigation and drainage. Four weeks old seedlings of variety BARI Tomato-2 (Ratan) were transplanted in the field on 9 November in Rangpur and 20 November in Gazipur. Ten seedlings were transplanted in each plot in two rows. Intercultural operations such as weeding, irrigation and mulching were done as and when necessary. Insect infestation was controlled by spraying Malathion 57 EC @ 0.15%.
Blight severity was recorded on a 0-5 scale from five plants selected randomly in each plot after 7 days of last spray and percent disease index (PDI) was calculated according to Meah (1994). Mature fruits were picked once or twice in a week and fruit number and fruit weight per plant were recorded. Fruit yield was expressed in ton per hectare. Plant height (cm) was recorded at the end of the crop period. All data were analyzed for ANOVA and means of the treatments were compared using MSTAT-C computer program.
RESULTS AND DISCUSSION
Under control plots, the maximum percent disease index (PDI) of 79.07 was observed in Gazipur, and 45.34 in Rangpur. Foliar spray with all of the fungicides resulted in significant reduction in disease severity over control. The reduction ranged 65-70% in Gazipur and 44-58% in Rangpur. The highest reduction in PDI was achieved with Rovral and Bicozeb. However, effectiveness of all fungicides to reduce disease severity was statistically similar (Table 1).
In Gazipur, plant height ranged 31-43 cm under different treatments including control. The plant height was minimal under control and maximum under Bicozeb followed by Rovral. The parameter under these two fungicides was statistically similar but significantly higher compared to control and other treatments. In Rangpur, plant height ranged 24-36 cm but none of the fungicides could produce any significant effect on this parameter compared to control (Table 1).
Under control, average fruit number per plant was 12.67 in Gazipur and 15.00 in Rangpur. Number of fruits per plant under different fungicide treatments ranged 14.34-34.05 in Gazipur and 15.05-35.95 in Rangpur. The fruit number was significantly higher under Rovral and Bicozeb compared to control in both the locations (Table 2).
In Gazipur, fruit yield under control was 65.83 t/ha, while those under different fungicide treatments ranged 71.25-83.75 t/ha. The yield was increased by 8-27% over control due to application of fungicides against early blight. The highest yield increase was obtained with Rovral and Bicozeb, which was followed by Pipertax and Media.
In Rangpur, the lowest yield of 50.03 t/ha was recorded from plots under control. Spraying with different fungicides increased the fruit yield to 52.10-78.75 t/ha. The increase in yield ranged 4 to 57% under different fungicides. The maximum yield increase was achieved with Rovral, which was followed by Bicozeb, Media and Pipertax (Table 2).
Results of the present study reveal that all the fungicides tested were effective to control early blight and improve plant growth and fruit yield of tomato. Among the fungicides, Rovral and Bicozeb provided better disease control and higher fruit yields compared to other fungicides.
Many investigators reported effectiveness of foliar spray with fungicides to control early blight of tomato (Nene and Thapliyal 1979), and Alternaria blights of mustard (Rahman 2000), cabbage (Hossain and Mian 2004), cauliflower (Kohinoor et al. 2003, Kudrati Khoda et al. 2003) and sunflower (Meah 1994). Considering the efficacy of different fungicides evaluated in the present study, Bicozeb may be suggested as an alternative to Rovral in controlling early blight of tomato.
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